Frangible fuse cap



June 23, 1970 D. o. MISARE FRANGIBLE FUSE CAP Filed April 22, 1968 FIG. I

E m Wm M W w r5 um E M 0 W; Z A N &W//// 7 I I I I I! I I I I I f I I! U ,w/ //M FRANGIBLE FUSE' CAP I 1 Donald 0. l\ /Ij'sare, Riverside, Ill., assignor to ,Ioslyn Mfg. and Supply Co., Chicago, 11]., a corporation of'lllinois Filed Apr. 22, 1968, Ser. No. 722,887 Int. Cl. H01h 39/00, 85/14 US. Cl. 337-203 4 Claims ABSTRACT on THE- DISCLOSURE- A rupturable cap for use on a fuse tube of the type open at one end having a fuse li'nk extending there through so as to provide for alteration ofthefuse-characteristics from a single-vented to a double-vented tube.- The fuse cap includes an internally threaded sleeve adapted for threaded engagement onto the fuse tube. The ap is closed with a thin disc of spring metal'held against a shoulder in the sleeve by a snap ring.

The present invention relates generally to an improved fuse construction, and'more'specifically to anew and improved fuse cap, particularly suitable as a frangible fuse cap adapted for dropout type fused cutouts foruse on high voltage electrical transmission lines.

Dropout type fuse circuits'are known which are adapt ed to interrupt both low amperage and high amperage faults equally well with conventional distribution fuse links. One known type of fuse construction provides al fuse cartridge structure for an open type fuse cutout. The cartridge includes-an open bottom or vent control arranged to provide single-venting of the'fuse cartridge on low current faults. The upper end of the fuse link contained within thecartridge is held in mechanical and electrical engagement with the upper terminal of the fuse cartridge by the fuse cap; iIt' hasv beenh'eretofore proposed that the fuse 'c'apberupturable upon a high-current'fault', uplto the maximumintr'rupting capacity of the cutout. Double-venting is obtaine'd by the provision of an expendable rupturable 'ca'p normally closing one end of the fuse cartridge. At a predetermined interrupting cur, rent, the cap will rupture both ends.

Difficulty has heretofore been experienced in the clarriping of the head of the fu'selink between the cap and the terminal on the fuse cartridge. Cold creep, andrepe'tiL A tive expansion and contraction under 'weather conditions, may cause mechanical and electrical loosening of the fuse cap head, accompanied by arcing, hot spots, radio interference and other difficulty.

Another difficulty frequently encountered with some prior types of expendable fuse caps is that slight excessive tightening of the cap by the lineman will rupture the expendable member and destroy the cap.

Moreover, although the cost of an individual cap is not too great, the caps are expendable and are sold in large quantities. The competitive situation requires the caps to be manufactured and sold at the least possible cost.

Additionally the caps must reliably rupture at an adequately predetermined pressure buildup within the fuse cartridge to insure uniform and continuous service of the fuse cartridge.

Accordingly it is. desirable to provide an improved fuse cartridge, and an improved fuse cap for the cartridge, which overcomes the above mentioned diificulties.

One object of the present invention is to provide a new improved fuse cap which possesses the above mentioned advantages.

Another object of the present invention is to provide a new and improved frangible fuse cap.

to vent the cartridge out of l a new and improved fuse cap which will maintain the.

.Patented June 23, 1970 Another object of the present invention is to provide head of-the fuse link tightly clamped electrically and mechanically with the terminal of the fuse cartridge.

f Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In accordance with these and many other objects of the present invention, there is provided an improved fuse construction, and a fuse cap for use on the fuse cartridge of the fuse construction, wherein the fuse cap is formed of an internally threaded sleeve closed with a thin disc of spring material such as of Phosphor bronze, and held in place by a snap ring locked in an internal groove in the sleeve.

Advantageously the new and improved cap spring loads the head of the fuse link against the fuse cartridge terminal and accordingly maintains a tight mechanical and FIG. 2 is a broken away isometric view of an improvedtarily illustrating the assemblyof the components of FIG.

electrical connection therewith substantially unaffected by repetitive expansions and contractions due to ambient conditions. Moreover the fuse cap may be tightened by a lineman without being readily ruptured by the lineman.

'The fuse cap may be cheaply and economically manufactured, and will rupture at a reliably accurate predetermined pressure buildup within the fuse cartridge to insure uniform and continuous service of the fuse cartridge.

Fora better understanding of the present invention,

'- reference may be had'to the accompanying drawings wherein:

FIG. 1 is an elevational view of a fuse assembly, employing an improved frangible fuse cap according to the present invention;

fuse capaccording to the present invention;

FIG. ,3 is an exploded isometric view of the fuse cap of FIG. 2; I

FIG. 4 is an elevational cross sectional view framen- 1, taken along line 44 of FIG. 1; and

FIG. 5 is an elevational sectional view similar to FIG. 4, but illustratesan explosive rupture of the fuse cap upon an abnormally highamperage fault.

7 Referring now to the drawings, particularly to FIG. 1 thereof-there is illustrated afuse assembly 10 according to the present invention. The fuse assembly 10 may be of a type known in the art, and, more specifically, may be similar to the fuse assembly more fully described in Letters Patent of the United States No. 2,862,080, assigned to the assignee of the present invention. Briefly, the fuse assembly 10 includes an elongated insulator 12 supported by a. suitable bracket 13 from a transmission line superstructure 14 which, in the instant case, is the crossarm of a high voltage tower. Upper and lower stationary terminal members 15 and 16 are carried at opposite ends of the insulator 12 for connection to the high voltage transmission line. The lower terminal member 16 is provided with a pair of trunnion supports in the form of hook members 18 which are spaced apart and which are provided with overhanging portions 19. The upper terminal member 15 is also provided with a suitable trunnion portion 20. The upper and lower terminal members 15' and 16 are provided with suitable means for connection to a high voltage transmission line.

A dropout fuse structure generally illustrated at 25 includes a fuse tube or cartridge 26. A downwardly and rearwardly extending arm 27 extends from the lower end of the fuse tube 26 and is provided with a cross trunnion 28 hooked in the hook members 18 to pivotally interconnect the fuse tube 26 to the lower terminal member 16.

The fuse structure 25 further includes an upper terminal 30 adapted to hook or engage within the trunnion portion 20 of the upper terminal member 15 to provide electrical contact with the fuse tube 26.

The fuse assembly is provided with a known fuse link 32 having a reduced fusible section 33 adjacent its upper end to provide for rupturing thereof in response to a fault in the power transmission circuit. Additionally, the upper end of the fuse link 32 is secured to a disc-shaped head 34 resting on the terminal 30. A washer 35 of brass or other electrically conductive material may be inter-- posed between the head 34 and the terminal 30. The upper end of the fuse link 32 extends through the open lower end of the fuse tube 26 and is secured to suitable spring structure 37 adapted to snap the fuse link 32 out of the tube 26 upon rupture of the fuse link 32.

In order to retain the upper end of the fuse link 32, the terminal 30 is provided with an upper threaded portion 38 having suitable external threads to receive a closure cap 40 according to the present invention. As best illustrated in 'FIGS. 2, 3, and 4, the closure cap 40 is formed of a sleeve 41, the lower end of which is internally threaded as at 41a, knurled on the outside. The upper end of the sleeve 41 is counterbored to provide a shoulder 42 at the upper end of the threaded portion 41a against which is seated a spring disc 43 of suitable spring material such as Phosphor bronze. The disc 43 is held in place by a snap ring 44 fitted into a groove 45- in the inner surface of the sleeve 41 just above the disc 42.

As illustrated in FIG. 4, the spring disc 42 maintains the head 35 of the fuse link 32 constantly in pressure engagement with the terminal 30 of the fuse cartridge, substantially unaffected by repetitive expansion and contraction of the parts. Moreover the disc 43 will be expelled from the cap 40 upon a sufficiently high, accurately determinable internal pressure within the fuse tube 26 upon a high current fault in the power transmission system.

Although the present invention has been described by reference to a single embodiment thereof, it will be apparent that numerous other modifications and embodiments will be devised by those skilled in the art which will fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A fuse construction comprising:

a fuse tube having a terminal structure at one end;

a fuse link capable of interruptions upon abnormal amperage faults, which link extends through the fuse tube and is provided with a disc-shaped head at one sleeve, bearing said head to spring load said head against said fuse 'ftube terminal, thereby maintaining a tight mechanical and electrical con nection therewith unaffected by repetitive ex- -pansions and contractions due to ambient conditions. I

2. A fuse construction as set forth in claim 1 including 7 a snap ring bearing against the outer edge of said disc and releasably locking said disc to said sleeve whereby said vdisc may be expelled from the cap upon a sufficiently high, accurately determined internal pressure within said tube. I v 1 3. A cap for use ona fuse tube of thetype open at one end having a fuse link extending therethrough, said cap comprising: an internally threaded sleeve, adisc of spring material transversely locked within said sleeve, and means to secure said disc within said sleeve.

4. A rupturable cap for use on a fuse tube of the type open at one end having a fuse link extending therethrough, said cap comprising: a sleeve internally threaded through at least a portion of its length, a circumferential shoulder defined within said sleeve on its inner surface above said threads, a disc of spring material positioned on said shoulder, said sleeve being provided with a circumferential channel on its inner surface adjacent said disc on the side remote from said shoulder, and a snap ring locked insaid channel and securing said disc within said sleeve. i

References Cited UNITED STATES PATENTS 2,583,440 1/1952 Orley et al 337277 2,702,842 2/1955 Jepsen et al. 337-223 2,846,214 4/ 1958 Wood 337-248 3,102,178 8/1963 Bronikowski 337-223 3,391,368 7/1968 Fahnoe 337-203 3,344,251 9/ 1967 Misare 337-203 FOREIGN PATENTS 566,191 12/ 1944 Great Britain.

HIRAM B. GILSQN, Primary Examiner US. Cl. X.R. 337248 

